1. Field of the Invention
The present invention relates to an optical apparatus for forming an object image on a solid-state image sensing element through a photographing optical member.
2. Description of the Related Art
In general, an optical apparatus using a solid-state image sensing element includes a zoom lens mechanism to obtain a desired photographing range.
The arrangement of the zoom lens mechanism of this optical apparatus will be described with reference to FIG. 27. FIG. 27 is a longitudinal sectional view showing the arrangement of the zoom lens mechanism of the conventional optical apparatus.
As shown in FIG. 27, the optical apparatus includes a plurality of lens groups constituted by a first lens group 101a, a second lens group 101b, a third lens group 101c, and a fourth lens group 101d. The second and fourth lens groups 101b and 101d are moved along the optical axis within predetermined ranges. The second lens group 101b is moved to perform a zooming operation. The fourth lens group 101d is moved to perform focus adjustment.
An optical low-pass filter 102 and a solid-state image sensing element 103 such as a CCD are sequentially arranged on the optical axis behind the fourth lens group 101d. 
The first lens group 101a, the third lens group 101c, the optical low-pass filter 102, the solid-state image sensing element 103, and the like are held in a housing 104.
The second lens group 101b is held in a optical holding member 105. The optical holding member 105 is supported to be movable along the optical axis on a guide pin 106 and a threaded member 107 which extend parallel along the optical axis. Each end portion of the guide pin 106 is supported on the housing 104.
The threaded member 107 has a threaded portion to be engaged with the optical holding member 105. Each end portion of the threaded member 107 is rotatably supported on the housing 104. A driving force from a stepping motor 110 is transferred to the threaded member 107 through a gear group 101. When the threaded member 107 is rotated by the driving force from the stepping motor 110, the optical holding member 105 is guided by the guide pin 106 and moved along the optical axis upon rotation of the threaded member 107. By moving the optical holding member 105, a zooming operation using the second lens group 101b is performed. The play between the threaded member 107 and the optical holding member 105 is removed by a biasing spring 108 and a biasing member 109.
Similar to the second lens group 101b, the fourth lens group 101d is supported in an optical holding member 116. The optical holding member 116 is supported to be movable along the optical axis on a guide pin 117 and a threaded member 113 which extend parallel along the optical axis. Each end portion of the guide pin 117 is supported on the housing 104.
The threaded member 113 has a threaded portion to be engaged with the optical holding member 116. One end portion of the threaded member 113 is rotatably supported on the housing 104. The other end portion of the threaded member 113 is rotatably supported on the housing 104 and directly connected to the output shaft of a stepping motor 112. When the threaded member 113 is rotated by a driving force from the stepping motor 112, the optical holding member 116 is guided by the guide pin 117 and moved along the optical axis upon rotation of the threaded member 113. By moving the optical holding member 116, focus adjustment using the fourth lens group 101d is performed. The play between the threaded member 113 and the optical holding member 116 is removed by the biasing spring 108 and the biasing member 109.
The moving positions of the second and fourth lens groups 101b and 101d, i.e., the moving positions of the optical holding members 105 and 116, are detected by position detection means (not shown). The detection amounts are used to control a zooming operation and a focus adjusting operation.
A stop 114 is disposed between the second lens group 101b and the third lens group 101c. The aperture of the stop 114 is adjusted by a driving force from a motor 115. The exposure amount is adjusted by this adjustment of the aperture of the stop 114.
With the recent advances in semiconductor chips such as memories and microcomputers, portable information devices have spread. Efforts have been made to further miniaturize such devices and improve their performance. Portability is a requirement for such portable information devices. Regarding the forms of the devices, a low profile is especially required.
These portable information devices include an optical apparatus for photographing an object image, information equipment including this optical apparatus, and the like. In order to obtain a low-profile optical apparatus, the overall thickness of the apparatus including a photographing optical system (a system constituted by, e.g., the lens groups, the stop, and the solid-state image sensing element in FIG. 27) and a mechanical system (a system constituted by, e.g., the gears and the motors which drive the lens groups, the motor which drives the stop, and the like in FIG. 27) must be decreased.
In the conventional optical apparatus, however, the first to fourth lens groups 101a to 101d, the optical low-pass filter 102, the solid-state image sensing element 103, and the like are held in the housing 104, and the motor 115 for driving the stop 114, the stepping motor 110 for driving the second lens group 101b, the stepping motor 112 for driving the fourth lens group 101d, and the like are held outside the housing 104. That is, the housing 104 has a three-dimensionally complicated shape. For this reason, the cost in manufacturing a housing mold generally using a plastic mold increases. In addition, sink marks, warpage, and the like are caused by partial heat shrinkage of the housing 104, and hence it is difficult to manufacture the housing 104 with high dimensional precision. Consequently, it is difficult to perform positioning of each lens group with respect to the solid-state image sensing element 103, positioning of each holding member, positioning of each position detection means, and the like with high precision. A slight relative positional offset caused between a given lens group and a corresponding position detection means makes it impossible to accurately detect the moving position of the lens group. As a result, blurring, fluctuations or the like of a photographed image may occur.
In addition, an electric circuit board on which drive circuits for the position detection means must be connected to the position detection means through lead wires or a flexible board. For this reason, mounting of such board and parts requires many steps, resulting in a complicated assembly operation.
Moreover, since the optical holding member 105 included in the mechanical system is generally supported to be symmetrical about the optical axis, the outer size of the housing 104 is large as compared with the lens system. Since the motors and the like are disposed outside the housing 104, the overall outer size of the apparatus further increases. It is, therefore, very difficult to decrease the dimension of the apparatus in the direction perpendicular to the optical axis, i.e., the thickness in the direction perpendicular to the optical axis.
The present applicant has proposed an optical apparatus which can easily realize a decrease in thickness by mounting a photographing optical system and a solid-state image sensing element on the same board.
In this proposed optical apparatus, however, the photographing optical system and the solid-state image sensing element must be positioned on the board with high precision to prevent deterioration in image quality, e.g., an image blur or fluctuation, caused by a relative offset between the mounting positions of the photographing optical system and the solid-state image sensing element. According to this requirement, a board capable of holding high flatness is needed.
If an actuator for driving a movable optical member included in the photographing optical system must be mounted on a board, the board must allow the actuator to be mounted thereon without interfering with a decrease in the thickness of the apparatus. As described above, a board suitable for all parts to be mounted thereon must be constituted.
In addition, since mechanical and electric parts must be mounted in various directions in assembling the apparatus, a cumbersome assembly operation is required, resulting in an increase in cost.
In order to solve these problems, an optical apparatus may be designed such that photographing optical members such as lenses are mounted on the board on which a solid-state image sensing element is mounted. With such an arrangement, a compact, low-profile optical apparatus can be realized at a low cost.
In this optical apparatus, however, since the photographing optical members such as lenses are mounted on the board on which the solid-state image sensing element is mounted, thermal deformation and mechanical deformation of the board will cause a relative positional offset between the solid-state image sensing element and the photographing optical member. As a result, the photographing optical member may tilt to cause deterioration in photographed images.
It is an object of the present invention to provide an optical apparatus which can decrease the overall thickness of the apparatus, and can reduce the influence of noise on a solid-state image sensing element.
It is another object of the present invention to provide an optical apparatus which can decrease the overall thickness of the apparatus, and can prevent deterioration in an image caused by a relative offset between the mounting positions of a photographing optical system and a solid-state image sensing element.
It is still another object of the present invention to provide an optical apparatus which can decrease the overall thickness of the apparatus by mounting parts, e.g., a photographing optical system, an actuator, a solid-state image sensing element, and electronic parts on a board, and allows the parts to be mounted on the board in accordance with mounting requirements.
It is still another object of the present invention to provide an optical apparatus which allows parts to be mounted on a board in accordance with mounting requirements.
It is still another object of the present invention to provide an optical apparatus which can prevent deterioration in photographed images caused by thermal deformation and mechanical deformation of a board.
Other features and advantages of the present invention will be apparent from the following description taken in conjunction with the accompanying drawings, in which like reference characters designate the same or similar parts throughout the figures thereof.